I say work-alike because the one I am considering (the A-One design from Achatz Electronics) is not really a clone as it uses modern parts. No longer available as a kit but all the firmware and documentation is available at http://www.achatz.nl/catalog/links.php. The parts are readily available. Sure I could use an emulator but melting solder is good.

I haven't build an Apple 1 work-alike, but I did build a Briel Altair 8800micro, which is an Altair 8800 work-alike. Vince Briel also sells his Replica-1 Apple 1 and Micro-KIM MOS KIM kits which are modern designs based on the originals. These are not clones or replicas - they use modern components and have many enhancements such as more RAM, PS/2 keyboard port and ATX PSU connector on the Replica-1.

My experience with Vince's kits having built two of them so far (The 8800micro and the 88-DSK RAM expansion) is that his kits are well built and designed to be easily built by people of any skill level. The instructions provided were clear and easy, though the kits are so well designed that the experienced builder will probably not need the instructions at all.

At $149 USD for the Replica-1 TE (3rd Edition) full kit I'm tempted to buy one just for the thrill of building it even though I have no particular interest in the Apple 1 itself.